dynamic accessibility nick poole ict adviser resource: the council for museums, archives and...

Dynamic AccessibilityNick PooleICT AdviserResource: The Council for Museums, Archives and Libraries

Contents

• Introduction• Static-page accessibility• Dynamic accessibility - key concepts• XHTML 1.1• Cascading Style Sheets• XML accessibility• New technologies - SMIL, VRML, SVG• e-Books and TTS• Contact details

Introduction

• What is accessibility?

• Technological accessibility

– browsers, platforms, operating systems, plugins, screen resolutions

• Intellectual accessibility

– navigation, language, structure, search tools, URL

• Physical accessibility

– design, layout, contrast, font size, text versions of animated/interactive information

Static-page accessibility

• Proper use of existing accessibility features in HTML

• Separation of content from presentation - CSS and ‘graceful transformation’

• Logical in-page reading order

• Logical in-site navigational structure

• Thinking about visual presentation - contrast, layout etc

• http://www.w3c/prg/WAI

Dynamic accessibility - key concepts

• Very similar...

• Separation of style from content

• Enabling dynamic re-flowing of content to address different platforms and technologies

• Clean code properly implemented

• The benefits and dangers of XML

• Making use of existing accessibility features

• Validate wherever possible

• Universal design and user-oriented publishing

XHTML 1.1• ‘The Extensible HyperText Markup Language (XHTML™) is a

family of current and future document types and modules that reproduce, subset, and extend HTML, reformulated In XML.’

• 3 ‘flavours’:

– strict - clean structural markup

– transitional - XHTML elements plus support for backwards-compatibility

– frameset - for creating pages subdivided into frames

XHTML 1.1 and Accessibility

• Well-formed XHTML pages follow a strict set of rules and avoid the use of non-standard markup

• XHTML supports graceful transformation between platforms - eg PC, PDA, braille

• Strict rule-based approach ensures better compatibility across browsers

• Imposes uniformity on document structure

• Keep pace with tech development

• Migrate existing documents from HTML using HTMLTidy - http://www.w3.org

Cascading Style Sheets

• CSS separates document structure (content) from presentation (style)

• Prevents the use of structural HTML tags to define layout

• Positioning properties avoid further use of markup to define layout

• Allows the user to override the server-side CSS with their own preferences

• Supports features which help orientation • Support for Aural Style Sheets (ACSS)• Better presentation of ALT content

XML Accessibility

• ‘An XML schema is accessible if it enables, and indeed actively promotes, the creation of accessible documents’

• …and

• ‘A document is accessible if it can be equally understood by its target audience regardless of the device used to access it’

‘XML Accessibility Guidelines’http://www.w3.org/TR/xag.html

XML Accessibility

• 2 key concepts:

• Semantic-rich schema that support accessibility

• Device independence - write once, deliver through different channels

XML Accessibility

• Facilitate the provision of ALT descriptions for different types of content– Apply the ‘summary’ and ‘caption’ elements

provided for tables in XHTML

<table border=“1” summary=“This table provides a list of names, addresses, telephone numbers and email addresses for club members”>

<caption><em>Contact details</em></caption>

<tr><th></tr><tr><td></tr></td>

</table>

XML Accessibility

• Standard mechanisms exist for linking and pointing in XML – Make use of XLink and Xpointer instead of

creating your own mechanisms (which may not be recognised/supported)

<crossref xmlns:xlink=“http://www.w3.org/1999/xlink”

xlink:href=“http://www.resource.gov.uk/file.xml”>

Link text

</crossref>

XML Accessibility

• Using the flexibility of XML to define element types that identify important text content– Certain elements are more important than others

in identifying and assessing the content of a document

– When creating a tagset, include semantic tags which allow you to identify these important elements

– In addition to identifying tags, include additional descriptive semantics

XML Accessibility

• When identifying important descriptive elements, make use of standard mechanisms/namespaces where possible (eg Dublin Core/RDF)

<rdf:RDF

xmlns:rdf=“http://www.w3.org/1999/02/22-rdf-syntax-ns#”

xmlns:dc=“http://www.purl.org/dc/elements/1.1/”>

<rdf:Description about =“http://www.peoplesnetwork.gov.uk”>

<dc:Title></dc.Title>

<dc:Description></dc.Description>

...etc...

XML Accessibility

• Semantic consistency

– Ensure that the same element contains the same content throughout the document - do not re-use elements for different purposes

– When re-using modules from elsewhere, ensure that you apply their elements as intended

XML Accessibility

• Using XML to design for platform-independence– Provide default style-sheets for output to different

platforms/devices (CSS or XSLT)– Create element types that allow classification and

grouping into logical, navigable document structures

– Provide ways of interacting with the document that are device-independent

– Allow the user to control the timeframe within which events occur

XML Accessibility

• Final points….– Document the semantics and structure of your

XML– Provide a machine-understandable way of

retrieving this documentation (eg. by using the xsi:schemaLocation attribute)

– Provide human-understandable definitions for the semantics of your XML elements (eg. by using the xsd:annotation attribute)

– Where accessible elements have been provided, ensure that these are documented

New technologies - SMIL

• Synchronised Multimedia Integration Language

• Specific issues:– Alternative equivalent content– Alternatives have to be synchronised with

primary media– Multiple sensory channels (sight, hearing, touch)– Content changes without user interaction leading

to disorientation

New Technologies - SMIL

• Alternative equivalent content– Text transcription - alt, title, abstract, longdesc– Auditory descriptions– Synchronised captions - textstream, system-

captions (where enabled)– Multilinguality - textstream captions in one

language, overdub audio descriptions in another– Use of the ‘switch’ element to allow the user to

select their preferred channel

New Technologies - SMIL

• Use SMIL in conjunction with CSS to provide screen layouts that transform (eg. percentage areas for onscreen captioning)

• Use the ‘title’ attribute to describe the nature of all SMIL elements

• Consider providing a ‘temporal’ navigation bar to enable user interaction with time-dependent content

• Use the ‘system-’ test attributes to re-purpose content to user preferences

New Technologies - VRML

• Range of built-in features to enhance access:– 2 levels of alternative textual description - ‘Worldinfo’ and

‘Anchor’ nodes– audio cues including spoken descriptions, proximity-

sensitive effects and trigger/viewpoint-specific events– mapping to external input devices to facilitate navigation

• Utilities available to enable access:– showVP, addSndToVrml and speakWorldInfo– essentially providing context/viewpoint info to assist the

user– http://ovrt.nist.gov/projects/VRMLaccess/

New Technologies - SVG

• Scalable Vector Graphics

• XML-based image format

• Range of accessibility features:– scalable!– Includes a text description for each logical component of

an image– images are encoded as plain text– SVG images can be encoded into XML documents– Can also call images from other documents using xLink– Images can be re-flowed to suit different media– Improved support for metadata

e-Books and Text-to-Speech

• Conflict between XML encoding and Digital Rights Management information

• XML encoding supports user-controlled text-to-speech delivery (Open e-Books Publication Structure)

• DRM protection blocks delivery through these channels

• Ongoing debate at: http://www.openebook.org

Contact:Nick Poole

ICT Adviser

Resource: The Council for Museums, Archives and Libraries

16 Queen Anne’s Gate

London SW1H 9AA

Email: nick.poole@resource.gov.uk

Web: http://www.peoplesnetwork.org.uk

Telephone: 020 7273 1410